Developing apparatus



July 11, 1961 s. w. JOHNSON DEVELOPING APPARATUS 3 Sheets-Sheet 1 Filed Feb. 6, 1959 INVENTOR. SIEURDW. Juz-msm July 11, 1961 s. w. JOHNSON DEVELOPING APPARATUS 3 Sheets-Sheet 2 Filed Feb. 6, 1959 INVENTOR. SIGURDW JDHNSDN Arroxwe) July 11, 1961 s. w. JOHNSON 2,991,754

DEVELOPING APPARATUS Filed Feb. 6, 1959 5 Sheets-Sheet 3 INVENTOR. SIGURDW. JUHNSUN United States Patent 2,991,754 DEVELOPLN G APPARATUS Sigurd W. Johnson, Oaklyn, N.J.. assignor to Radio Corporation of America, a corporation of Delaware Filed Feb. 6, 1959, Ser. No. 791,676 12 Claims. (Cl. 118-637) This invention relates generally to developing apparatus and more particularly to apparatus for developing electrostatic latent images of the type produced in the electrophotographic art.

The developing apparatus of the present invention is particularly useful for developing electrostatic latent images by means of liquid developers.

It has been proposed to develop electrostatic latent images produced on record members, in accordance with the electrophotograpnic methods, by means of liquid developers contained in tanks or in dishes. In such prior art developing methods, the exposed record member with its latent image thereon was immersed in the tank or dish containing the liquid developer for a predetermined period of time, thereby wetting both sides of the record member. While such prior art methods have been used satisfactorily for developing small record members, it has been relatively more difiicult to develop larger record members and/or a continuous web of exposed record material by such methods.

Accordingly, it is an object of the present invention to provide improved developing apparatus for developing electrostatic latent images with a liquid developer.

Another object of the present invention is to provide novel developing apparatus for developing an electrostatic latent image on one side of a record member by applying liquid developer only to the exposed side of the record member.

Still another object of the present invention is to pro vide improved developing apparatus whereby the application of liquid developer to a record member may be mechanically controlled.

A further object of the present invention is to provide novel developing apparatus for applying a liquid developer to only one side of an exposed record member in a plurality of stages and concentrations.

Still a further object of the present invention is to provide improved developing apparatus for developing electrostatic latent images on record members quickly, precisely, and automatically.

In accordance with the present invention, the foregoing objects and related advantages are attained in improved and novel developing apparatus adapted to apply a suitable liquid developer to one side of exposed record members in controlled amounts. The novel developing apparatus, in one embodiment, comprises a pair of feed rollers and a pair of squeegee rollers adapted to direct an exposed record member over the surface of a toner roller. The toner roller and one of the pair of squeegee rollers are made to revolve in a tray of liquid developer so as to carry the liquid developer to the exposed surface of the record member. Adjusting means comprising a tension belt are associated with the feed rollers in a manner to vary the dihedral angle between the plane defined by the axes of the feed rollers and the plane defined by the axes of the squeegee rollers. By this adjusting means, it is possible to cause the record member to pass over the toner roller so that the exposed surface of the record member will contact the liquid developer on the toner roller without touching the toner roller itself. Thus, for example, the record member may be made to travel in an are over the toner roller while being displaced, say, about 0.003 inch, from the toner roller.

In another embodiment of the novel developing apparatus of the present invention, at least two toner rollers are used. A separate tray of liquid developer, each of a different concentration, is provided for each roller. It has been found that excellent electrophotographic prints may be obtained by first applying a concentrated liquid developer to the exposed record image with one toner roller and then by applying a less concentrated developer to the record member with at least one other subsequent toner roller.

The novel features of the present invention, as well as the invention itself, both as to its organization and methods of operation, will be understood in detail when considered in connection with the accompanying drawings in which similar reference characters represent similar parts and in which:

FIG. 1 is a perspective view of the novel developing apparatus, in accordance with the present invention, showing the front, right side, and top of the apparatus;

FIG. 2 is a right side elevational view, with parts broken away, of the developing apparatus;

FIG. 3 is a fragmentary rear view of the developing apparatus showing details of the developer tray holding means;

FIG. 4 is a fragmentary perspective rear view of the developing apparatus showing additional details of the developer tray holding means; and

FIG. 5 is a right side elevational view of a portion of another embodiment of the novel developing apparatus of the present invention.

Referring now to FIGURES 1, 2, and 3 the developing apparatus 10 of the present invention is shown supported on a base 12. Separate upright beams 14, 16, 1S and 20 extend upwardly from each of the corners of the rectangular base 12. The upright beams 14, 16, 18, and 20 are secured to the base 12 by any suitable means, as by welding, for example. The upper portions of the beams 16 and 18 are secured to the ends of a horizontal beam 22 by any suitable means. Similarly, the ends of a horizontal beam 24 are secured to the upper portions of the beams 14 and 20. A front horizontal beam 26 is secured to the upper portions of the upright beams 14 and 16 by any suitable means.

The ends of a shaft 28 of a horizontally disposed toner roller 30 are journaled in the rearward portions of the horizontal beams 22 and 24, respectively. The toner roller 30 may he chromium plated brass. The toner roller 30 has its lower portion disposed within a developer tray 32. The developer tray 32 is adapted to hold a suitable liquid developer 33 comprising a toner powder freely dispersed Within a suitable liquid. Examples of suitable liquid developers for developing an electrostatic latent image on a record member by the apparatus of the present invention are described in the Journal of Scientific Instruments, volume 32, February 1955, pages 74 and 75.

A variable speed motor 34 is mounted on the base 12 for the purpose of rotating the toner roller 30 in a counterclockwise direction, as indicated by the arrow on the toner roller 30, looking at FIG. 2. A pulley 36 geared to the shaft of the motor 34 is coupled to a pulley 38 fixed to the shaft 28 of the toner roller 30 by means of a belt 40. A lever 42 associated with the variable speed mechanism 44 of the variable speed motor 34 controls the speed of rotation of the toner roller 30. It will now be understood that the toner roller 30 may be made to rotate in the liquid developer 33 in the developer tray 32 at any speed chosen by the position of the speed control levers 42. The motor 34 may be operated by means of a toggle switch 46, disposed on the front horizontal beam 26 and electrically wired to the motor 34.

Means are provided to feed a record member 50 over the toner roller 30 to develop an electrostatic latent image on the lower surface of the record member 50. To this end, a pair of feed rollers 52 and 54 are provided. The

3 lower feed roller 52 has a horizontally disposed shaft 56 whose ends are journaled in the side horizontal beams 22 and 24.

A plurality of similar belts 58 are looped around the lower feed roller 52. The belts 58 are also looped around individual pulleys 60 disposed on a shaft 62 in an evenly spaced apart relationship. The pulleys 60 may rotate freely around the fixed shaft 62.

The upper feed roller 54 rests on the belts 58. The shaft 64 of the feed roller 54 is disposed parallel to the horizontal shaft 56 of the lower feed roller 52, but is ofiset forwardly from the shaft 56 so that the plane defined by the shafts 64 and 56 forms an acute dihedral angle with a vertical plane.

The upper feed roller 54 is adapted to move vertically in accordance with the amount of tension placed on the belts 58. The ends of the shaft 64 of the upper feed roller 54 are journaled in horizontally disposed blocks 66 and 67. Vertical through openings adjacent the ends of the block 66 receive pin 68 and 70 that extend upwardly from the horizontal beam 22. Similarly, the block 67 is movable in a vertical direction by having vertical holes therein receive pins 72 and 74 that extend upwardly from the horizontal beam 24. The blocks 66 and 67 may be considered slidably mounted on the vertically disposed pairs of pins 68 and 70 and 72 and 74, respectively. It will now be understood that the dihedral angle formed by the plane including the shafts 64 and 56 and the vertical plane is a function of the tension on the belts 58.

Each of a pair of adjusting screws 76 and 78 threadedly engaged in the forward end of the horizontal beams 24 and 22, respectively, provides means for adjusting the tension on the belts 58. The ends of the shaft 62 are disposed in horizontal slits 80 in the forward ends of the horizontal beams 22 and 24. The screws 76 and 78 are in threaded engagement transversely through the ends of the shaft 62. Thus, by turning the screws 76 and 78 in one direction, the shaft 62 is pulled forward, and tension on the belts 58 is increased. T his increase in tension on the belts 58 will serve to raise the upper feed roller 54 since the roller 54 rests on the belts 58. Conversely, turning the screws 76 and 78 in an opposite direction, the shaft 62 will move rearwardly and tension on the belts 58 will decrease. This will result in the upper feed roller 54 moving in a downward position. The upper feed roller 54 may be made of rubber, and the lower feed roller 52 may be made of brass.

A pair of upper and lower squeegee rollers 82 and 84 are disposed rearwardly of the toner roller 30. The lower squeegee roller 84 has a shaft 86 whose ends are journaled in the horizontal beams 22 and 24. The upper squeegee roller 82 has a shaft 83 journaled in blocks 88 and 90. Each of the blocks 88 and 90 has a pair of vertical through openings adapted to receive a pair of upwardly extending pins 92 and 94 and 96 and 98, respectively. The pairs of pins 92 and 94 and 96 and 98 are fixed to the upper rear portions of the horizontal beams 22 and 24, respectively, by any suitable means.

The upper squeegee roller 82 may be made of rubber and the lower squeegee roller 84 may be made of brass. A cross-bar 100 has a pair of vertical holes therein adapted to slide over pins 92 and 94 extending upwardly, and fixed to the horizontal beam 22. Threaded screws 102 and 104 in the cross-bar 100, and adapted to engage the pins 92 and 94, may position the cross-bar 100 in any fixed position above the block 88. A spring 106 disposed between the cross-bar 100 and the block 88 provides the necessary pressure of the upper squeegee roller 82 against the lower squeegee roller 84. A similar arrangement on the left side of the squeegee rollers 82 and 84 is provided.

The lower feed roller 52 and the lower squeegee roller 84 are adapted to be rotated in the same direction at the same speed. Thus, a variable speed motor 108 is fixed to the base 12 by any suitable means. A pulley 110,fixed to the shaft-of the motor 108, turns a pulley 112 fixed to the shaft 86 of the lower squeegee roller 84, by means of a belt 114. Another pulley 116 fixed to the shaft 86 is coupled to a pulley 118 fixed to the shaft 56 of the lower feeder roller 52. The pulleys 116 and 118 are of the same diameter and are coupled to each other by means of a belt 120. Thus, the speed of rotation of similar rollers 52 and 84 will be the same and in the same direction.

Looking at FIG. 2, it will be seen that if the pulley of the motor 108 turns in a clockwise direction, the lower squeegee roller 84 and the lower feed roller 52 will also turn in the same direction and with the same speed. A lever 122 controls the speed of the motor 108 by any suitable gearing arrangement. The motor 108 may be controlled by a toggle switch 124, fixed to the front horizontal beam 26, and wired to the motor 108. The developer tray 32 extends below the lower squeegee roller 84 for purposes hereinafter appearing.

Referring now to FIGURES 3 and 4, means are shown for retaining the liquid developer tray 32 in the developing apparatus 10. The tray 32 is fixed to two parallelly disposed bars and 132 beneath the tray 32 by any suitable means. A separate block of a pair of blocks 134 and 136 are fixed to the rear inner surfaces of the horizontal beams 22 and 24. Each of the blocks 134 and 136 are formed with similar parallel grooves 138 and 140. The ends of the rods 130 and 132 are adapted to slide in the grooves 138 and 140. A pair of spaced apart vertical grooves 142 and 144 are formed in the upper portion of the blocks 134, as shown in FIGURE 4. The vertical grooves 142 and 144 communicate with the horizontal groove 138. .The block 136 is similarly formed.

A spring biased hinge 146 has a lower portion secured to the lower portion of the block 134 and the upper portion urging the rods 130 and 132 upwardly into the grooves 142 and 144. An arm 148 on the upper portion of the hinge 146 extends rearwardly and inwardly for the purpose of enabling one to manipulate the hinge 146 in order to lower or raise the developer tray 32. A hinge 150, similar to the hinge 146, is fixed to the block 136 and serves the same function as the hinge 146.

The operation of the developing apparatus 10 will now be described. The record member 50 to be developed is placed with the latent image facing downwardly on the upper runs of the belts 58. The toggle switches 46 and 124 are energized and the speed of the motors 108 and 34 are adjusted. It has been found that very satisfactory results of developing can be obtained by having the toner roller rotate up to speeds just below that which will produce turbulence of the liquid developer 33. The speed of advancing the record member 50 over the toner roller 30 is usually one-half the speed of rotation of the toner roller 30.

The screws 76 and 78 are adjusted to put proper tension on the belts 58 so that the record member 50' will move between the feeder rollers 52 and 54 at the proper angle. The dihedral angle of the planes defined by the axes 64 and 56 of the feeder rollers and the plane defined by the axes 83 and 86 of the squeegee rollers determines the radius of curvature of the are made by the record member 50 over the toner roller 30. By a proper adjustment of the screws 76 and 78 suitable tension is applied to the similar belts 58, and the record member 50 will advance over the toner roller 30 and between the squeegee rollers 82 and 84. It has been found that the latent image of a record member may be developed satisfactorily by having the record member 50 displaced about 0.003 inch above the toner roller 30. The liquid toner adhering to the toner roller 30 may now contact and develop the record member 50 without touching the toner roller 30. In FIG. 2, the dotted line 152 shows the path of travel of a record member 50 when fed over the toner roller 30 by means of the feeder rollers and the squeegee rollers.

With the arrangement of apparatus shown in FIG- URES l, 2, 3 and 4, it is possible to apply liquid developer 33 from the tray 32 to the latent image on the record member 50 both by the toner roller 30 and by the lower squeegee roller 84. The developed record member 50 emerging from between the squeegee rollers 82 and 84 may be dried by heating, or if self-drying toner developer 33 is used the developed image will be ready for handling as soon as it is dried.

Referring now to FIG. 5, there is shown another embodiment a of the developing apparatus, in accordance with the present invention, wherein similar reference characters represent similar parts. The developing apparatus in FIG. 5 differs from the developing apparatus 10 previously described in that an additional toner roller 30a is provided. The toner roller 30a is adapted to rotate in the same direction as the toner roller 30 by means of a belt 156 linking pulleys 154 and 154a fixed to the shafts of these rollers. A tray 32a is provided for the toner roller 30a. With such an arrangement, the liquid developer in the developer tray 32a may be of a different concentration from the liquid developer in the developer tray 32. It has been found that very satisfactory results can be obtained by first developing the record member 50 in a concentrated liquid developer, which may be in the tray 32a, and then by developing in a less concentrated developer by means of the toner roller 30 and the squeegee roller 84 from the developer tray 32. The curvature of the are 152, representing the path the record member 50 will take when advanced between the squeegee rollers and the feed rollers is determined by the tension adjustments provided by the screws 76 and 78, as explained for the developing apparatus 10.

From the foregoing description, it will be apparent that there has been provided improved apparatus for developing electrostatic latent images with liquid developer. While some of the apparatus has been shown in diagrammatic form, various components useful therein, as well as variation in the apparatus itself, coming within the spirit of this invention, will no doubt, readily suggest themselves to those skilled in the art. Hence it is desired that the foregoing shall be considered merely as illustrative and not in a limiting sense.

What is claimed is:

1. Apparatus for developing an electrostatic image on a record member with a liquid developer dispersion comprising a pair of feed rollers, a pair of squeegee rollers so positioned with respect to said feed rollers that the plane defined by the axes of said feed rollers forms a dihedral angle with the plane defined by the axes of said squeegee rollers, a toner roller disposed between said pair of feed rollers and said pair of squeegee rollers, means to apply said liquid developer dispersion to said toner roller, means to rotate said feed rollers and said squeegee rollers to move said record member therebetween and over said toner roller, means to rotate said toner roller, the axes of said rollers being substantially parallel to each other, and means to change the dihedral angle between the plane defined by the axes of said pair of feed rollers and the plane defined by the axes of said pair of squeegee rollers.

2. Apparatus for developing an electrostatic image on a record member with a liquid developer dispersion comprising a pair of feed rollers having upper and lower rollers, 21 pair of squeegee rollers having upper and lower rollers so positioned with respect to said feed rollers that the plane defined by the axes of said feed rollers forms a dihedral angle with the plane defined by the axes of said squeegee rollers, a toner roller disposed between said pair of feed rollers and said pair of squeegee rollers, means to position a container of said liquid developer dispersion beneath said toner roller and said lower roller of said pair of squeegee rollers, said toner roller being positioned at least partially within said container, means to rotate said feed rollers and said squeegee rollers to move said record member therebetween and over said toner rollers, means to rotate said toner roller in a direction opposite to the direction of rotation of said lower rollers and at a greater speed than said lower rollers, the axes of said rollers being substantially parallel to each other, and means to change the dihedral angle between the plane defined by the axes of said pair of feed rollers and the plane defined by the axes of said pair of squeegee rollers whereby to vary the distance between said record member and said toner roller.

3. Apparatus for developing an electrostatic image on a record member with a liquid developer dispersion comprising a pair of feed rollers, a pair of squeegee rollers so positioned with respect to said feed rollers that the plane defined by the axes of said feed rollers forms a dihedral angle with the plane defined by the axes of said squeegee rollers, at least two toner rollers disposed between said pair of feed rollers and said pair of squeegee rollers, means to apply liquid developer dispersion to said toner roller nearest to said feed rollers, means to apply liquid developer dispersion to at least one of said toner rollers, means to rotate said feed rollers and said squeegee rollers to move said record member therebetween and over said toner rollers, means to rotate said toner rollers, the axes of said rollers being substantially parallel to each other, and means to change the dihedral angle between the plane defined by the axes of said pair of feed rollers and the plane defined by the axes of said pair of squeegee rollers.

4. Apparatus for developing an electrostatic image on a record member with a liquid developer dispersion comprising a pair of feed rollers having upper and lower rollers, a pair of squeegee rollers having upper and lower rollers so positioned with respect to said feed rollers that the plane defined by the axes of said feed rollers forms a dihedral angle with the plane defined by the axes of said squeegee rollers, at least two toner rollers disposed between said pair of feed rollers and said pair of squeegee rollers, means to position a first container of said liquid developer dispersion beneath said toner roller nearest to said feed rollers, means to position a second container of said liquid developer dispersion beneath said toner roller nearest to said squeegee rollers and said lower roller of said squeegee rollers, each said toner roller being positioned at least partially within its associated container, means to rotate said feed rollers and said squeegee rollers to move said record member therebetween and over said toner rollers, means to rotate said toner rollers in a direction opposite to the direction of rotation of said lower rollers, the axes of said rollers being substantially parallel to each other, means to change the dihedral angle between the plane defined by the axes of said pair of feed rollers and the plane defined by the axes of said pair of squeegee rollers.

5. Apparatus comprising a pair of feed rollers having upper and lower rollers, belt means disposed around said lower roller, a pair of squeegee rollers having upper and lower rollers, a toner roller disposed between said lower roller of said pair of feed rollers and said lower roller of said pair of squeegee rollers, means to rotate said lower rollers in one direction, means to rotate said toner roller in an opposite direction, means to dispose a container of liquid toner dispersion beneath said toner roller whereby said toner roller will rotate therein, said upper roller of said pair of feed rollers resting on said belt means, means to vary the tension on said belt means, and means to guide said upper roller of said pair of feed rollers for movement in a substantially vertical plane in accordance with the tension on said belt means.

6. Apparatus comprising a pair of feed rollers having upper and lower rollers, belt means disposed around said lower roller, a pair of squeegee rollers having upper and lower rollers, a toner roller disposed between said lower roller of said pair of feed rollers and said lower roller of said pair of squeegee rollers, means to rotate said lower rollers in one direction, means to rotate said toner roller in an opposite direction, means to apply a liquid toner dispersion to said toner roller, said upper roller of said pair of feed rollers resting on said belt means, means to vary the tension on said belt means, and means to guide said upper roller of said pair of feed rollers for movement in a substantially vertical plane in accordance with the tension on said belt means.

7. Apparatus comprising a pair of feed rollers having upper and lower rollers, belt means disposed around said lower roller, a pair of squeegee rollers having upper and lower rollers, at least two toner rollers disposed between said lower roller of said pair of feed rollers and said lower roller of said pair of squeegee rollers, means to rotate said lower rollers in one direction, means to rotate said toner rollers in an opposite direction, means to dispose a separate container of liquid toner dispersion beneath each of said toner rollers whereby said toner rollers will rotate there in, said upper roller of said pair of feed rollers resting on said belt means, means to vary the tension on said belt means, and means to guide said upper roller of said pair of feed rollers for movement in a substantially vertical plane in accordance with the tension on said belt means.

8. Apparatus comprising a pair of feed rollers having upper and lower rollers, belt means disposed around said lower roller, a pair of squeegee rollers so positioned with respect to said feed rollers that the plane defined by the axes of said feed rollers forms a dihedral angle with the plane defined by the axe of said squeegee rollers having upper and lower rollers, a toner roller diposed between said lower roller of said pair of feed rollers and said lower roller of said pair of squeegee rollers, means to rotate said lower rollers in one direction, means to rotate said toner roller in an opposite direction and at a faster speed than said lower rollers, means to apply liquid toner dispersion to said toner roller and to said lower roller of sad squeegee rollers, said upper roller of said feed rollers resting on said belt means, means to vary the tension on said belt means, and means to guide said upper roller of said pair of feed rollers for movement in a substantially vertical plane in accordance with the tension on said belt means.

9. Developing apparatus comp-rising a pair of plates fixed in a spaced apart relationship to each other, a horizontally disposed toner roller positioned between said plates and having a shaft whose ends are journaled in said plates a pair of feed rollers including a lower roller disposed between said plates and to one side of said toner roller and having a shaft whose ends are journaled in said plates, a pair of squeegee rollers including a lower roller disposed between said plates and to an opposite side of said toner roller and having a shaft Whose ends are journaled in said plates, said feed rollers and said squeegee rollers being so positioned that the plane defined by the axes of said feed rollers forms a dihedral angle with the plane defined by the axes of said squeegee rollers means to rotate said lower rollers in one direction and means to rotate said toner roller in an opposite direction to said one direction, belt means around said lower roller of said pair of feed rollers, said feed rollers including an upper roller resting on said belt means, means to vary the tension on said belt means, means to guide said upper roller of said feed rollers for movement in a substantially verticle plane in accordance with the tension on said belt means, the axes of said pair of said feed rollers defining a plane forming an acute dihedral angle with the plane defined by the axes of said pair of squeegee rollers, means to position a container beneath said toner roller and said lower roller of said pair of squeegee rollers.

10. Developing apparatus comprising a pair of substantially parallel plates fixed in a spaced apart relationship to each other, a pair of horizontally disposed toner rollers positioned between said plates and having shafts whose ends are journaled in said parallel plates, a pair of feed rollers including a lower roller disposed between said plates and to one side of one of said pair of toner rollers and having a shaft whose ends are journaled in said plates, a pair of squeegee rollers including a lower roller disposed between said plates and to one side of the other of said pair of toner rollers and having a shaft whose ends are journaled in said plates, means to rotate said lower rollers in one direction, and means to rotate said toner rollers in an opposite direction to said one direction, belt means around said lower roller of said pair of feed rollers, said feed rollers including an upper roller resting on said belt means, means to vary the tension of said belt means, means to guide said upper roller of said pair of feed rollers for movement in a substantially verticle plane in accordance with the tension on said belt means, the axes of said pair of said feed rollers defining a plane forming an acute dihedral angle with the plane defined by the axes of said pair of squeegee rollers, means to position a separate container beneath each of said toner rollers.

11. Sheet material feeding apparatus comprising: a pair of feed rollers; a pair of pressure rollers so positioned with respect to said feed rollers that the plane defined by the axes of said feed rollers forms a dihedral angle with the plane defined by the axes of said pressure rollers; an applicator member, said member having a surface capable of retaining thereon matter to be applied to said sheet material, disposed between said pair of feed rollers and said pair of pressure rollers; means for rotating said feed rollers and said pressure rollers to move said sheet material therebetween and adjacent said applicator member; and means for adjusting the dihedral angle between the planes defined by the axes of said pair of feed rollers and said pair of pressure rollers to prevent direct contact of said sheet material with said applicator member, but to contact said matter thereon.

:12. Apparatus for developing an electrostatic image on a record member with a liquid developer dispersion; said apparatus comprising: a pair of feed rollers, a pair of squeegee rollers so positioned with respect to said feed rollers that the plane defined by the axes of said feed rollers forms a dihedral angle with the plane defined by the axes of said squeegee rollers, a toner roller disposed between said pair of feed rollers and said pair of squeegee rollers and in substantially parallel relation thereto, means for applying liquid developer dispersion to said toner roller, means for rotating said feed rollers and said squeegee rollers to move a record member therebetween, means for rotating said toner roller to bring liquid developer dispersion carried thereon into contact with said record member, and means to adjust the dihedral angle between the plane defined by the axes of said pair of feed rollers and the plane defined by the axes of said pair of squeegee rollers to a value such as to cause said record member to pass over said toner roller and to contact the liquid developer dispersion thereon without contacting said toner roller.

References Cited in the file of this patent UNITED STATES PATENTS 920,367 Morse May 4, 1909 1,926,363 Bergstein Sept. 12, 1933 2,877,133 Mayer Mar. 10, 1959 

